Continuously variable transmissions of the type wherein a belt is passed on drive and driven pulleys have been proposed and put into practical use. The belt includes an endless (loop-shaped) steel belt or cylindrical ring which is formed by laminating a plurality of endless steel sheets. A plurality of steel elements are supported on the ring in a manner to be aligned along the periphery of the ring so that the adjacent ones are contactable with each other. Each pulley includes axially movable and fixed wheel counterparts which are coaxial with and face each other to define therebetween a pulley groove. The axially movable wheel counterpart is axially movable under an axial thrust of a controlled hydraulic pressure so as to change the width of the pulley groove. A clearance is formed between the adjacent elements of the belt owing to an initial clearance and extension of the steel band. This clearance causes the belt to slip relative to the belt. Such a slip is remarkable particularly at a low gear (large transmission ratio) and reaches to several % to several tens %. This slip of the belt cannot be suppressed under changing transmission ratio even if a predetermined axial thrust is applied to the movable wheel counterpart to put the belt between the movable and fixed wheel counterparts of the pulley under a pressure. As a result, the continuously variable transmissions of this type are degraded in durability and power transmission efficiency.